Multiple window scanner and method for adjusting optical parameters

ABSTRACT

A multiple window data reading device and method for reading symbols such as bar codes through each window, including sensing conditions from each window and adjusting optical parameters for controlling data reading control through each of the windows.

CONTINUING APPLICATION DATA

This application is a divisional of application Ser. No. 09/206,665,filed Dec. 7, 1998, now U.S. Pat. No. 6,213,397, which is a divisionalof application Ser. No. 08/912,891 filed Aug. 15, 1997 U.S. Pat. No.5,869,827, which is a continuation of application Ser. No. 08/461,047filed Jun. 5, 1995 U.S. Pat. No. 5,723,852, which is a divisional ofapplication Ser. No. 08/188,164 filed Jan. 26, 1994 U.S. Pat. No.5,491,328, which is a continuation-in-part of application Ser. No.08/108,112 filed Aug. 17, 1993, abandoned, which is a divisional ofapplication Ser. No. 07/764,527 filed Sep. 24, 1991 U.S. Pat. No.5,256,864.

BACKGROUND OF THE INVENTION

The field of the present invention generally relates to bar codescanning apparatus. More particularly, the field of the presentinvention relates to a method and apparatus for preferentially aligningthe surfaces of an item with respect to a predetermined locus ofpositions defining an optimal scanning path for decoding a bar codelabel and a system for providing display of alphanumeric data and/orpictorial images or the like corresponding to the item being scanned.

Bar code scanners are well known for scanning the universal product code(“UPC”) and other types of bar codes on packages or containers,particularly in retail stores. Generally, in retail stores, bar codescanners are set up at check-out stands or are built into a horizontalcheck-out counter so that a laser beam is scanned up through atransparent window, defining a number of different scan lines. Normally,packages are placed by the customer on a counter, deck or conveyor. Acheck-out person then takes each package, visually locates the UPC orother bar code label on a surface of the package and moves the packagethrough the laser's scanning area. One disadvantage of this technique isthat the label must first be found and then the package must be held ina particular orientation in order to effect an accurate reading by thelaser scanner decoding the bar code lines as the bar code moves throughthe scanning area. Misalignment of the bar code lines, or inadvertentmovement of the package during the scanning operation can result in amisreading (or a non-read) of the bar code.

Conventional attempts to minimize or eliminate the participation ofcheck-out personnel include a device such as described in U.S. Pat. No.4,939,355. There, an item transported by a moving conveyor is subjectedto a complex series of different scan patterns approaching fromdifferent sides of the item. This scanning requires a large depth offield for the scan beams. The item to be scanned is placed in anyorientation on the scan belt. A scanning means generates scan lines inan X configuration for reading the object in virtually any orientation.Due to the infinite variations in product sizes, irregularities ofshapes and differing locations of a bar code label on an item,conventional scanning methods too frequently fail to achieve a firstsuccessful read on the pass of the item scanned, which requiresrescanning to obtain the data associated with the bar code label beingdecoded.

Additionally, conventional methods for bar code scanning provide thecustomer with an itemized listing, such as receipt list, of the itemswhich were scanned. There is a time lag between the time that the itemsare scanned and the point at which the customer receives the itemizedlist. This time lag often results in a lack of customer recognition ofthe items and their associated prices. The lack of recognition inherentin a list, disassociated from the items as they are moving on a scanningpath, may lead to customer misunderstanding and may slow down thecheck-out process at a retail point of sale.

Another problem associated with conventional automated scanning systemsinvolves security. For example, in the method described in U.S. Pat. No.4,676,343, the customer must look for each label and then scans the itemin the conventional manner. The item is then placed on a conveyor beltfor transport and item verification. This system is very slow because ofthe inexperience of the customer and because of the difficulty infinding the label. This method also does not provide adequate securitybecause the customer can place a higher priced similar item on the belt.

An additional problem in a conventional automated scanning system is asubstantial number of “no reads” when an item is not positioned properlyin the scanning region. When an item has an irregularly shaped surface,the rate of no-reads tends to be higher for conventional automaticscanning systems.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to a data reading systemand a method for data reading. In a preferred configuration, the datareading system, such as a bar code scanner, includes a scanner housing;a plurality of surfaces facing a scan volume; and sets of patternmirrors positioned adjacent the respective surfaces, the housing beingconstructed to have at least a portion thereof positioned above the scanvolume. In one embodiment, the housing contains a single scanningmechanism for producing scanning beams which are routed to the patternmirrors and out through the respective surfaces into the scan volume. Inanother embodiment, the housing contains a multiple beam source forgenerating a plurality of laser beams which are routed to the patternmirrors and out through the respective surfaces into the scan volume.

According to another embodiment, the bar code scanning system providesan improved through-put such as may be used in a checker-less retailcheckout for scanning a bar code label on at least two surfaces of anitem moving along an item path and through a scanning region.

According to another embodiment, a transporter moves an item along anitem path and through a scanning region wherein the focal plane of alaser scanner is automatically oriented in optimal coplanar alignmentwith a surface of the item being scanned. The transporter may comprise afirst belt having a surface for moving the item along the item path anda second belt disposed substantially at 90° to the first belt and movingin a parallel direction. The belts are preferably tilted atapproximately 30° to the horizontal so that an item placed on eitherbelt will have at least two surfaces stably registered by gravity, onesurface to each supporting surface of the belt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an overall system;

FIG. 1A is a schematic drawing showing how unread items may be returnedto a customer for rescanning or manual check-out;

FIG. 2 is a front view showing scanning through the belts of the system;

FIG. 3 is a top view of the preferred spacing of slots between O-ringsfor admitting scanning lines;

FIG. 4A is a perspective view of another embodiment of the presentinvention showing a stationary guide means;

FIG. 4B is a perspective view of another embodiment of the presentinvention using a moving platen;

FIG. 4C is a perspective view of another embodiment of the presentinvention using two plates of transparent material;

FIG. 5A is a schematic view of the height sensing apparatus to anembodiment of the present invention;

FIG. 5B is a schematic view of height and width sensing in accordancewith an embodiment of the present invention;

FIG. 5C is a schematic view of a checkout system including a robotsorter and packager;

FIG. 6A is a top plan view of one system for generating a scanningpattern for scanning the non-belt contacting sides of the packagegenerally parallel to the belts' surfaces;

FIG. 6B is a schematic side view of another system of generating ascanning pattern for scanning the front and back faces of the package;

FIG. 6C is a perspective view showing a first arrangement for generatingslot specific lines;

FIG. 6D is a perspective view showing another arrangement for generatingslot specific lines;

FIG. 6E is a schematic drawing of a conventional means forretro-directive collection in conventional bar codes scanners;

FIG. 6F is a schematic drawing of the light collection method with thedepth of focus enhancement method;

FIG. 6G is a schematic drawing of the light collection method using twolaser sources in the same scanning system;

FIG. 6H is a top plan view of an alternate embodiment to the system ofFIG. 6A which generates multiple scanning patterns and multipledistances;

FIG. 6I is a schematic top plan view of a simplified version of thesystem of FIG. 6A which generates multiple scanning patterns;

FIG. 6J is a schematic side view of the system of FIG. 6I;

FIG. 6K is a schematic top plan view of another simplified version ofthe system of FIG. 6A which generates multiple scanning patterns;

FIG. 6L is a schematic side view of the system of FIG. 6K;

FIG. 6M is a diagrammatic view of the system of FIGS. 6K and 6Lpositioned in the housing of FIG. 2;

FIG. 7A is a perspective view showing an apparatus for generating avisual display image on a thermochromic material or the like;

FIG. 7B is a detail of the heating roller of FIG. 7A;

FIG. 7C is a detail of the circuit for the heating roller of FIG. 7B;

FIG. 7D is a detail of the circuit for the heating roller of FIG. 7A;

FIG. 8A is a perspective view of an apparatus for activating a patternof pixels for creating a display image;

FIG. 8B is a schematic diagram of NCAP liquid crystal display film; and

FIG. 8C is a schematic circuit diagram for the LCD film of FIG. 8B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments will now be described with respect to thedrawings. FIG. 1 shows a system for preferentially aligning andregistering at least two surfaces of a package for optimally scanning abar code label located on those surfaces. In the automatic scanningsystem, as shown in FIG. 1, items are placed on a transport meanscomprising a belt 1 for scanning one item at a time. One or more itemgates 2 may be provided for sensing the beginning and end of each item.The items are conveyed by the belt 1 into a scanning region 4. Anaperture 3 initially provides a means for achieving a generalpreferential orientation of an item with respect to height and width sothat the item will be generally positioned on the belt 1 for scanning aswill be explained. A visual display 5 of data relating to the item beingscanned moves along a belt or other display means concurrently and inproximity with the item. This visual display enhances customer andsecurity personnel recognition and association of pricing data and otherinformation with the item as it moves along the item path through thescanning region. This display may also be used to instruct the customerand to verify pricing for each item.

The present inventors have recognized it may be desirable to have asystem for completely stabilizing an item as it is moved along an itempath through a scanning region. It may also be desirable to register twosurfaces of an item to be scanned such that the bar code labels arepreferentially positioned in a predetermined, optimal alignment with thescanning lines of a laser bar code scanner. At least two surfaces of apackage to be scanned are located such that the two surfaces are stablyregistered with respect to a predetermined locus of positions whichdefine an optimal scanning path for a bar code scanner.

A bar code label may be optimally scanned to increase the first passread rate thereby facilitating the checking out of items at a point ofsale such as a grocery market check-out area. In this regard, a systemmay optimally scan bar code labels on surfaces of an item which arestabilized with respect to an optimal scanning path and which limits thenumber of directions from which the surfaces of an item are scanned.This system advantageously would simplify the scanning process andincrease the speed and accuracy of the scanning.

FIG. 1A is a top view of an arrangement wherein conveyor belts can beused to return items with unread labels to the customer. In normaloperation, the customer places the items on the input belt 1. Thepresence and size of the item in one dimension are measured by the itemgate 2 or other item gates along the belt 1. Next, the item moves intothe scanning region 4 where the scanned laser beams attempt to read thebar code label. If the item label is read, a read signal is sent to thebelt control system, (not shown) in accordance with well-knowntechniques. After the item has passed scanning region 4, a section oftwo belts 6 can rotate so as to form a joint with a normal singlehorizontal conveyor belt. A conveyor belt 7 is directed perpendicular tothe rotated conveyor belt 6. This belt can direct the items which werecorrectly read to the storage area 8. A downward sloping ramp 9 conductsthe items into the storage area 8. By reversing the direction of belt 7,items which are not read can be sent back to the customer on anotherbelt 10. These unread items are collected on a shelf 11 at the end ofthe return belt 10. The customer can then place the unread item on theinput belt 1 again or carry the item to the pay station where theattendant can read the label in a conventional manner.

As shown in FIG. 2, the system facilitates the check-out of groceries orother items traveling along an item path and through a scanning regiondefined by scanning lines 18 a, 18 b. A transport means preferablycomprises conveyor belts 20, 22 which orient two surfaces of a packagein a preferential alignment so that a bar code label is registered in anoptimal position for reading by a scanning bar code reader as showngenerally at 24 a and 24 b in FIG. 2. A package to be read rests in atrough formed by the two conveyor belts 20 and 22 which are preferablyaligned at 90° to one another. This alignment locates two surfaces ofmost packages and registers a respective surface of a package to eachbelt. Further, the orthogonal belt combination 20, 22 is tipped at someangle such that the items contact a surface of the belt 22 and slide dueto the force of gravity against the other belt. This configurationenables an automatic preferential alignment of two surfaces of the itemto be scanned against respective contacting surfaces of the belts 20 and22. Because the belts 20 and 22 move in unison, the two surfaces of theitem are substantially registered in an invariant alignment with respectto a scanning means.

Each face of the scanned volume is scanned separately from a separatedirection as well. The belts limit the scanning of a bar code label on abelt-contact surface to only two scan directions; along the belt andperpendicular to it. A laser scanning means generates a series ofparallel scanning lines which describe a scanning volume in a firstdirection perpendicular to the first belt. Because the belts are alignedat 90° to each other, at least two generally orthogonally opposedsurfaces of the item to be scanned are registered stably by gravity, orby vibration assisted sliding, against a respective surface of the belt.This automatically aligns the scanning bars of the bar code on a firstsurface of the object with the focal plane of scanning lines which scanthe object in a first direction perpendicular to the belt. The scanningmeans produces a series of scanning lines in a second scanning directionperpendicular to the second belt and thus to the second surface of theitem registered to the second belt. Thus, the scanning bars of the barcode label of the second surface of the item are also automaticallyaligned in a coplanar orientation with the focal planes of the scanninglines produced in the second direction.

In the foregoing double tilted belt design, the items are automaticallyaligned in an optimal direction for the scanning bars which generallyrun parallel to the package or item edges. Because of the motion of thebelt, a single vertical scan line and an array of horizontal scan linesare sufficient to read a of bar code label on either the first or secondsurfaces of the belt. This aspect of the present invention achieves afirst pass read rate of bar code labels greater than 95%. Such a firstpass read rate was heretofore unlikely due to the limitations ofconventional scanning devices mentioned above.

As shown in FIG. 2, the two surfaces of an item 26 are oriented andlocated in a predetermined plane for reading with the scanning lines 18a and 18 b of a scanning means 24 a and 24 b such as a bar code scanner.This orientation enables the items to be stabilized in accordance with apredetermined, optimal plane, coplanar with a scanning plane for readingthe bar code label. This configuration of two conveyor belts moving inconcert may be used in manned check-out systems or in partially or fullyautomated check-out systems.

In accordance with the embodiment as shown in FIG. 2, bar code labels 25on the surfaces of an item 26 which are in contact or in close proximitywith belts 20 and 22 are scanned through a series of slot means disposedin belts 20 and 22. The slot means define slot specific scanning linesat an optimal plane with respect to the item surfaces registered to thebelts. It will be appreciated that the scanning lines 18 a and 18 b scanthe item in accordance with a predetermined locus of positions whichalso define an optimal scanning path or focal plane for sensing anddecoding a bar code label.

In a preferred embodiment, as shown in FIG. 2, at least two scannermeans 24 are disposed for scanning a separate surface of the item 26through the spaces 28 in the belts 22 and 20 respectively. The belts 20and 22 limit the scanning to only two scan directions as shown. A firstscanning means 24 a is disposed substantially orthogonally with respectto the first belt 20 for scanning a corresponding surface of the item 26disposed on the belt 20. A second scanning means 24 b is disposedorthogonally with respect to the second belt 22 for scanning acorresponding surface of an item 26 registered to belt 22.

In another embodiment, the scanning is accomplished through slot meansor spaces 28 disposed in the belt in recurrent rows parallel to thedirection of the belt for defining a focal scanning plane coplanar withitem surfaces which are registered to the belts. The scanning lines 18defined by the slot means 28 may be optimally aligned with the parallelbars of a bar code label disposed on either of the major surfaces ofitem 26 which are registered to belts 20 and 22, respectively.

Referring to FIG. 3, in another embodiment, scanning is done through aseries of slot means or spaces 28 disposed in the belts 20 and 22,respectively, for defining an optimal locus of positions for scanninglines at the item surface. In a preferred embodiment, slot means 28comprise a series of O-rings or a plurality of thin flat belts arrangedin recurrent rows parallel to the direction of the belts for definingscanning lines at the item surface parallel to the belt. As shown inFIG. 3, scan slots and scan lines 36 are parallel to the O-ring or thinflat belt. One or more scanning lines 34 may be provided perpendicularto the belt. In the instance where both belts are tilted from thehorizontal and vertical as in FIG. 2, an item 26 will be preferentiallyaligned (by gravitational action) in an optimal direction for scanningthe bars of a bar code label 25 which run parallel to the package edges.Because of the motion of the belt, a single vertical line 34 and anarray of horizontal scanning lines 36 are sufficient.

The scanning lines 34 and 36 may be defined by either O-rings or byslots in a belt or by a belt including a series of smaller parallelbelts or a plurality of thin flat belts for creating a desired spacingfor admitting scanning lines. FIG. 3 shows a pattern for the example ofa 12 inch wide section of belt 20 or 22. In a preferred embodiment,there are a total of 40 horizontal lines on a 0.3 inch spacing. Thisfeature of the invention enables the scanning lines 18 to beautomatically aligned in an optimal focal plane with the scanning barsof a bar code label 25 on both surfaces of an item 26 which areregistered to the belts 20 and 22. Other belt widths, belt spacing andscan slot lengths can be chosen without departing from the principles ofthe invention.

Alternatively, scanning may be carried out through a transparent plateof material such as scratch resistant glass. The transparent plate isdisposed such that the O-rings or thin belts move the item across theplates. The focal plane of the scanning lines is coplanar with the glassplate and with the lines of the item bar code label as it moves acrossthe plate. Scanning also may be done through a transparent scratchresistant belt, without the need for O-rings or slots.

A decoding means (not shown) for decoding the scattered light signalgenerated by the scanning means is provided in accordance with wellknown techniques. The decoding means includes a microprocessor forproducing an output signal representative of the data derived from thescanning of the bar code label in accordance with well known techniques.

Referring to FIGS. 4A and 4B, an alternate embodiment of the presentinvention provides a means for automatically orienting an item andaligning at least two surfaces with respect to a predetermined locus ofpositions for defining an optimal scanning path for decoding a bar codelabel. In FIG. 4A, a means for preferentially aligning an item surfacealong a moving belt 40 is provided by a platen 42. The platen 42 has aguide surface 43 disposed at 90° with respect to a moving belt 40. Thebelt and platen may be tipped from the horizontal and vertical positionto automatically align a surface of the item against the platen 42 andbelt 40 by gravity. Also, vibration assisted registration of surfaces ofthe item may be employed to stabilize a planar surface of the item to arespective belt. Alternatively, a customer may place a surface of theitem against the platen 42 and thereby preferentially align at least twosurfaces of the item to be scanned. One surface of an item 45 isautomatically oriented, being substantially invariantly stabilized andaligned by gravity for scanning against the belt 40. The other surfaceis aligned against the platen 42 by gravity when the scanned surfacesare tilted. The guide surface 43 of the platen 42 is preferablycomprised of a slick material having a low coefficient of friction suchas teflon. A series of scan lines 46, 47 are scanned through the platen42 and through the belt 40, respectively. The scan lines 46, 47 runparallel to the package edges and parallel to the direction of the belt.Accordingly, the scanning lines are preferentially aligned in an optimalfocal plane coplanar with the bars of the bar code label which also runparallel to the package edges. A single scan line 36 a or 36 b isarranged to scan perpendicular to belt motion through a narrow slot ateither belt end 40.

As shown in FIG. 4B, a moving platen 48 similar to the slots 44 a in thebelt 40 may be provided which travels in concert with the belt 40 andmoves the item along the item path in a predetermined, optimal alignmentwith the scanning lines of a bar code scanner. A series of spaces orthrough-slots 44 b also may be provided in the moving platen 48 foroptimally scanning a bar code label of the item adjacent thereto.

The bar and space elements of a bar code label of a first surface of theitem adjacent the guide means are automatically positioned in an optimalcoplanar relation with the scanning lines of a bar code scanner whichscans the bar code labels through slots or spaces in the supportingplaten. Similarly, the bar and space elements of a bar code label on thesurface of the item adjacent the orthogonal supporting transport beltare automatically positioned in an optimum coplanar relation with thescanning lines produced by the bar code scanner which scans the bar codelabel from a perpendicular direction through slots or spaces in thesupporting transport belt.

In an alternate embodiment of FIG. 4C, two plates 49, 49 a oftransparent material, preferably scratch resistant glass, are disposedat substantially 90 degrees to one another. Together, the plates 49, 49a form a trough which defines an item path for preferentially aligningtwo faces of an item in a predetermined position, coplanar with therespective focal planes of scanning lines produced by a scanning means.Any convenient motive means, such as transport belts or vibrationassisted sliding is provided for moving an item along the path formed bythe glass plates. Scanning is done through the glass plates 49, 49 a.The focal plane of the scanning lines being coplanar with the plane ofthe glass. In this way, a face of the item is stably registered againsta corresponding plate such that the lines of one bar code label arepreferentially aligned in a coplanar orientation with the scanning linesfrom a bar code scanner, resulting in a mechanically simplified scanningmeans. Alternately, a transparent scratch resistant belt can be used asthe supporting medium, and scanning can be done through the transparentbelt.

Referring to FIG. 5A, means are provided for automatically establishingthe optimal location of the scanning beam waist for resolving a bar codeon item surfaces not in contact with either belt. This mechanism isimportant because the location of the bar code label surface can varydepending upon the size of the package. For example in a typical grocerycheckout application, in the height direction, the surface location mayvary from 0 to 8 inches. In the width direction, the surface locationmay vary from 0 to 12 inches. A typical four inch depth of focus as isused in many conventional scanning devices is insufficient to cover thisrange. In a preferred embodiment, the limiting location of the labelsurface in the height and width direction is determined by thedimensions of the scanning aperture 14 (FIG. 1) which serves as a roughinitial orientation of a package surface to be placed on the transportmeans 12.

Because the label can be located on any surface, the surfaces not incontact with the belts must be separately scanned. These surfaces not incontact with the orthogonal belts can be at a wide variety of positionsand angles. An ideal depth of focus may be established for reading thebar codes of symmetric items on surfaces parallel to the belt surfaces,but not in contact, on items of varying widths and heights. Accordingly,a first laser beam source produces a beam waist sufficiently focused toresolve elements of a bar code of an item greater than a predeterminedwidth. The first laser beam source is focused on half of the volumeabove the orthogonal belt. A second laser beam source is also focused onthe other half of the volume above the orthogonal belts for producing abeam waist sufficiently focused and scanned to resolve elements of a barcode on the surfaces of an object smaller than a predetermined width. Asensor means associated with the first and second laser beam sources isprovided for sensing when an item greater than a predetermined width andheight is about to be scanned. The sensor means activates the firstlaser beam source when a large object over the threshold width andheight is to be scanned. The sensor means deactivates the first laserbeam source and activates the second laser beam source when an objectsmaller than the threshold size is sensed. Each item surface above thebelts is advantageously scanned according to its location. And, becausetwo surfaces of the object being scanned are stably registered bygravity against the supporting surface of orthogonal belts, this aspectestablishes an ideal depth of focus for resolving a bar code label ofobjects of varying size. In a similar manner a third and fourth lasersource, disposed orthogonally to the first and second laser sources,scan the front and back surfaces (relative to belt motion) of an item toproduce an optimally focused scanning plane. This scanning is done fromthe top with the beams that scan a pre-set angular range relative to thebelt. Since the package is moving toward and away from the respectivesets of scan lines, ample time is available for scanning.

In another embodiment, two laser sources may be scanned within the samescanning mirrors in conjunction with two detectors. In this case, thetwo laser beams produce two beams which are close enough to each otherto be scanned by the same mirrored polygon and pattern mirrors, but farenough from each other in angle to be imaged in two different locationsby the collection lens. Each beam therefore, has its own waist locationand detector. In this method, the beams may be multiplexed with theircorresponding detectors for producing a single data stream.Alternatively, the beams may be used simultaneously for producing twodata streams. To obtain an increase in the effective depth of focus, thetwo beams can be focused at different distances.

Scanning will be simplified in comparison to conventional devices and atthe same time achieves an optimal alignment of an item bar code labelwith the scanning lines of a scanning means. This greatly enhances thefirst pass read rate in comparison with conventional devices. Anenhanced accuracy rate is especially possible for items whose bar codelabels are parallel or perpendicular to the package edges. Scanning islimited to two directions wherein two surfaces of the item to be scannedare automatically oriented and in focus at a predetermined plane forenabling the scanning bars of a bar code label to optimally read by abar code scanner. Sensing the package cross-section perpendicular to thepackage motion also enables the depth of focus of the scanning beams tobe optimized. This configuration further enhances the costeffectiveness, speed and accuracy of scanning items at a retail point ofsale or the like. The need for a checker at a point of sale may beeliminated, thereby providing a primary economic motivation for theimplementation of the present system. To insure a useful scanning spotsize over the approximate eight inch depth, a measuring light beam isprojected across the aperture to a detector as shown in FIG. 5A. Theprojector 50 consists preferably of an LED and a lens. The detector 52consists of a lens and a photodetector. The measuring light beamdetermines if the height of a package is greater or less than apredetermined height, for example four inches. The required laser module(e.g. far lasers 65 a, 65 b and near lasers 65 c, 65 d as shown in FIG.6A) is then turned on as needed. The two polarized beams are combinedwithin a respective polarizing cube 67 a, 67 b, consequently there is nopower loss. Since the laser beams are aligned, the detector is always inthe correct position. A first laser beam source (either far laser 65 aor 65 b) produces a beam waist sufficiently focused to scan and resolvea bar code of an item greater than a predetermined size, for example aheight of four inches. A second laser beam source (either near laser 65c or 65 d) produces a beam waist sufficiently focused to scan andresolve a bar code of an object smaller than a predetermined size.

The optical projector and detector 50, 52, respectively, of FIG. 5Acomprise sensor means which are associated in accordance with well knowntechniques with the first and second laser beam sources. The LEDprojector 50 and detector 52 are coupled with the laser beam sources foractivating the first beam source when an item greater than apredetermined size is sensed (the beam from 50 does not reach detector52). The sensor means then activate the second beam source when anobject smaller than a predetermined size is sensed. This aspectoptimizes the depth of focus for resolving bar code labels on objects ofdifferent sizes. This feature combines with other aspects to provide avery high first pass read rate of bar code labels.

As shown in FIG. 5B, a third and fourth laser source are provided forscanning the height as well as the width of the front and back of apackage. Thus, the focal planes of the scanning lines are optimized forheight as well as width.

It will be appreciated that the foregoing technique may be used in asimilar manner in the 12 inch direction wherein the depth of focus mustbe extended from four inches to six inches. This can be accomplished byusing a larger spot size and higher laser power in accordance with wellknown techniques.

According to another embodiment, the foregoing features make possiblethe implementation of a fully automated, servo-controlled robotpackaging system for sorting, bagging, or packaging items according totheir size, weight or other desired parameters. Referring to FIG. 5C,items are placed upon a belt 1 where they are preferentially positionedby a guide means 500 so as to be in an optimal focal plane for scanningby a bar code scanning means as previously explained. Guide means 500may be a platen or an orthogonally disposed moving belt as set forthabove. The items then move along the item path defined by the belt 1through a scanning region 4. Scanners 502 a and 502 b scan the items inthe scanning region in accordance with well-known techniques aspreviously explained. The scanners 502 a and 502 b resolve the bar codelabels as described above, and in accordance with well known techniques,produce a decoding signal representative of the information contained inthe bar code label. Preferably, scanners 502 a and 502 b include meansfor sensing dimensional parameters of an item which are necessary forfacilitating packaging and bagging, such as height, width, weight, orthe like.

The controller means 504 is responsive to the decoding signalscontaining the bar code information and dimensional data of items beingscanned. The controller means 504 in turn activates a robot sorter means506 which sorts and packages each of the items in accordance with theinformation derived from the respective bar code label from that item.The controller means 504 is also responsive to signals from an item gate(not shown) and takes into account the belt speed to activate the robotsorter means 506 at the appropriate time as the item moves along theitem path in accordance with well-known techniques. The robot sortermeans then sorts each item according to size and weight and bags orotherwise appropriately packages the item.

Referring now to FIGS. 6A and 6B, another embodiment provides a singlemulti-faceted mirror polygon 60 for generating at least two scanpatterns for scanning the surface of a package from different directions(in the illustrated embodiment, opposite directions are illustrated) inaccordance with a predetermined locus of positions which define anoptimal scanning plane congruent with the surfaces of the packageregistered to the belts.

Referring to FIGS. 6A and 6B, the multiple lasers (65 a-d) provide formultiple waist distances and multiple scan directions operating off thesame rotating mirror polygon 60. Top far laser 65 a and top near laser65 c (focused at respective far and near distances) each produces alaser beam which passes through the polarizing cube 67 a, and isdirected off one side of the mirror polygon 60 which scans the beamsacross the pattern mirrors 62 a. Similarly, the side far laser 65 b andside near laser 65 d (focused at respective far and near distances) eachproduces a laser beam which passes through the polarizing cube 67 b, andis directed off another side of the mirror polygon 60 which scans thebeams across the pattern mirrors 62 b.

In a preferred embodiment, the optimal scan patterns are generated witha single eight-sided mirror polygon 60 with each mirror facet tipped ata desired angle in accordance with well known techniques. Patternmirrors 62 a, 62 b similar to those used on the bottom and side scannersmay be used on the top and free side. A desired number of scan lines,for example eight scan lines, reflect off five long mirrors and therebycreate 40 scan lines. The single scanning means (shown in this exampleas mirror polygon 60) can be used to scan two (or more) sides of theitem through both sides of the titled belt conveyor (see FIG. 2). Otherarrangements of pattern mirrors well known in the industry can be usedto scan these faces. The scanning mirror 60, in combination with otherfeatures described, ensures that the focal plane of a laser scanner isautomatically aligned in a coplanar relation with respect to a surfaceof the item to be scanned. In addition, a single decoding means coulddecode the return signal from both scan patterns. The decoding means istypically a conventional decoding circuit which is well known in theart.

The same mirror polygon 60 can be used to scan both free end faces of apackage on the titled belt conveyor system. As shown in FIG. 6B, thelaser beams reflect off the mirror polygon 60 and pattern mirrors 63 aand 63 b respectively, to produce the scanning volume 64 along theconveyor belt 66 as shown. The scanning volume 64 contains the surfacesof the item to be scanned which is registered in a predeterminedlocation on the conveyor belt 66 as previously explained. The lasermodules and pattern mirrors of FIG. 6A are not shown in 6B.

Referring to FIG. 6B, the scan pattern is relatively simple to generatebecause the package is moving in the direction to bring the beam in andout of focus. At a belt speed of eight inches per second, a four inchdepth of focus allows ½ second of time for scanning. Because bothsurfaces of the object which are registered to the orthogonally disposedbelts are scanned at the same time, this arrangement allows sufficienttime for both the front and back package faces to be adequately scanned.

The system described uses several lasers and scan pattern generators,modules and multiple sets of front-end electronics. There are manystreams of data to be analyzed. The decoding may be consolidated intotwo or perhaps one decoder board. Schemes well known in the art can beused to produce a unique, unambiguous decoder signal for each itemscanned.

FIGS. 6C and 6D show the preferred method for generating theslot-specific scanning lines. The faces of the mirror polygon 60 in 6Ccan each be set at a different angle relative to the axis of the motorand rotated about a circumference producing an array of parallel linesshown on the display screen. This screen 62 is used for the purpose ofdescription only and does not exist in the scanner.

In FIG. 6D, a laser module generates a beam 61 being directed ontomirrored polygon 60 having a plurality of mirror facets 60 a, 60 a toform the scan beams 61 a. Each mirror 63 and subsequent mirrors formingthe pattern mirror array 65 are tilted slightly to segment the scanlines and to direct them to the slots between the belts. The other scanlines required are generated using scan lines which miss mirrors 65 andstrike other mirrors using techniques which are well known in theindustry. Thus, it can be seen that slot-specific scan lines areproduced initially by a reflection from a mirrored polygon 60 having apredetermined number (N) of facets, and secondly by a reflection from anarray of mirrors 65, wherein the number of mirrors in the array may bedesignated by M. This arrangement will produce M times N lines which aresubstantially parallel, but which are spaced apart from one another. Thespace between the scan lines may be selected by tilting the polygonfacets of the mirror polygon 60 and the mirrors of the array 65.

FIGS. 6E, 6F and 6G show details of three reflected light collectionsystems. In the conventional system shown in FIG. 6E, the input laserbeam 602 is reflected along the axis of a lens 601 and through theoptical system by the small mirror 603. A portion of the light reflectedby the label is imaged by the lens 601 onto the detector 604. Theangular orientation of the outgoing laser is such that the spot isalways imaged on the detector.

In FIG. 6F polarized laser sources 607 and 608 are combined withsubstantially no loss in the polarizing beam splitter 606. To ensurethat the light reflected from the label is imaged onto the samedetector, the two laser beams must be substantially parallel to eachother. In this embodiment, the appropriate laser beam is switched on bythe item sizing sensing method described with respect to FIG. 5.

FIG. 6G shows the detail of a further embodiment in which two laserbeams can be used alternately or simultaneously. Each laser beam 607 and608 is reflected generally along the axis of the lens 601 by mirrors611. The angular separation of the beams is small enough that the beamsare both contained within the scanning mirrors yet they are separatedwith respect to their angles far enough to be detected by the twoseparate detectors 609 and 610. This configuration advantageously allowsscanning of a greater volume with multiple depths of focus, without theneed for a beam splitter. For example, one beam may have a depth offocus in a range of from 10-12 inches, while the other beam may have adepth of focus of 12-14 inches.

FIG. 6H illustrates an alternate embodiment to the multiple scanningdirection, multiple focus distance system of FIG. 6A. In the system 150of FIG. 6H, only two lasers are used, far laser 165 a providing thefurther distant waist location and near laser 165 b providing the nearerdistant waist location. The far laser 165 a generates a laser beamtoward a beam splitter 169 which splits the beam into two components, afirst portion of the beam being directed to a first side of the mirrorpolygon 160 and a second portion of the beam being directed to a foldmirror 170 which reflects it onto a second side of the mirror polygon.Similarly, the near laser 165 b generates a laser beam toward a beamsplitter 168 which splits the beam into two components, a first portionof the beam being directed to the second side of the mirror polygon 160and a second portion of the beam being directed to a fold mirror 167which reflects it onto the first side of the mirror polygon 160. Themirror polygon 160 scans the first portion of the far laser beam and thesecond portion of the near laser beam off of the pattern mirrors 162 awhile simultaneously scanning the second portion of the far laser beamand the first portion of the near laser beam off of the pattern mirrors162 b and creating a desired pattern of intersecting lines (ornon-intersecting lines if desired) into the scanning volume.

FIGS. 6I and 6J illustrate a simplified embodiment of the system of FIG.6A only including multidirection scanning. The system 250 of FIGS. 6Iand 6J uses a single scanning means comprised of a mirror polygon 260rotatably driven by a motor 259. The system 250 includes a first laserbeam 270 generated by a first laser source 265 a and a second laser beam271 generated by a second laser source 265 a. The first and second laserbeams 270, 271 are directed onto the mirror polygon 260 in a planenonparallel to an axis of rotation of the mirror polygon 260. The firstlaser beam 270 is reflected off a fold mirror 267 and off a first sideof the mirror polygon 260 and scanned across the pattern mirrors 262.FIG. 6J illustrates one pair of mirrors. 262 a and 262 b (there would ofcourse preferably be a pattern mirror or pattern mirror combination foreach facet of the mirror polygon 260) which operate together to directthe first beam 270 into the scan volume 264. In similar fashion, thesecond laser beam 271 is reflected off fold mirror 268 and off a secondside of the mirror polygon 260 and scanned across the pattern mirrors263. FIG. 6J illustrates one pair of mirrors 263 a and 263 b whichoperate together to direct the second beam 271 into the scan volume 264.One skilled in the art may design a desired angles of mirror facets ofthe mirror polygon 260 and the angles and locations of the patternmirrors 262, 263 to achieve the desired scan pattern within the scanvolume 264.

FIGS. 6K and 6L illustrate another simplified embodiment of the systemof FIG. 6A. The system 350 of FIGS. 6K and 6L uses a single scanningmeans comprised of a mirror polygon 360 rotatably driven by a motor 359.The system 350 includes a first and second laser beams 370, 371generated by a single laser source 365. The laser source 365 generates alaser beam 375 which is divided by a beam splitter 367 into the firstand second laser beams 370, 371. The first laser beam 370 is reflectedoff a first side of the mirror polygon 360 and scanned across thepattern mirror set 362. FIG. 6L illustrates a single pattern mirror 362a into the scan volume 364. Scanning beams from different facets of themirror polygon 360 would reflect off the other pattern mirrors 362 b,362 c. In similar fashion, the second laser beam 371 is reflected off afold mirror 368 and off a second side of the mirror polygon 360 andscanned across the pattern mirror set 363. FIG. 6J illustrates one pairof mirrors 263 a and 263 b which operate together to direct the secondbeam 271 into the scan volume 264. One skilled in the art may design adesired angles of mirror facets of the mirror polygon 360 and the anglesand locations of the sets of pattern mirrors 362, 363 to achieve thedesired scan pattern within the scan volume 364.

FIG. 6M illustrates one possible multiplanar scanning system 450 inwhich the scanning system 350 of FIGS. 6K-6L is disposed in the housingof FIG. 2. The elements of the scanning system are located in a centralsection of the housing 440 with the first set of pattern mirrors 462 a-cbeing located in a first side housing portion 442 and the second set ofpattern mirrors 463 a-c being located in a second side housing portion444. The system 450 uses a single scanning means comprised of a mirrorpolygon 460 rotatably driven by a motor 459. The system 450 includes afirst and second laser beams 470, 471 generated by a single laser source465. The laser source 465 generates a laser beam which is divided by abeam splitter 467 into the first and second laser beams 470, 471. Thefirst laser beam 470 is reflected off a first side of the mirror polygon460 and scanned across the first set of pattern mirrors 462 a-c and outthe window 443 into the scan volume. The second laser beam 471 reflectsoff a fold mirror 468 is reflected off a second side of the mirrorpolygon 460 and scanned across the second set of pattern mirrors 463 a-cand out the window 445 into the scan volume. It may be noted that thewindows 443 and 445 are arranged generally orthogonally to allow forfull scan coverage of the item being scanned.

Referring to FIGS. 2 and 6M, though these figures illustrate each of thesurfaces being inclined at about 45° from the horizontal, it ispreferred that each surface is oriented at least 30° from horizontalwhile maintaining the 90° relationship therebetween.

In accordance with another preferred embodiment, a display means isprovided which is responsive to the output signal of a scanning meansfor providing a concurrently moving display of data relating to the itembeing scanned. The display means comprises an alphanumeric display(and/or graphical display such as descriptive or pictorial) positionedpreferably along as the conveyor belt or at any convenient location fordisplaying the price and other data directly next to the item beingpurchased. The display is preferably located proximate the item path sothat the user may readily associate the display data with the item beingmoved down the item path. Referring again to FIG. 1, as an item movesdown the transport belt 1, the price and name or other related datamoves concurrently with the item in a display 5. This advantageouslyenables a customer to see what he is being charged for the item as it ismoving down the belt. To be most useful, a long display (about fourfeet) with two rows of characters may be needed. Other messages to thecustomer also may be communicated with such a display.

Several display technologies are appropriate for this purpose. Theyinclude light emitting diodes (LEDs) and liquid crystal displays (LCDs).An LED array may be programmed to move the alphanumeric data at the beltspeed and in alignment with the item being decoded. Preferably, thedisplay is located near the belt so that the customer is provided withan instantaneous alphanumeric display of data corresponding to each itembeing scanned. However, LED and conventional LCD displays may beexpensive to use in such an application. The lower cost LCD display alsomay be too slow for high belt speed and may necessitate a slower thanoptimal transport speed for the transport means.

Therefore, in a preferred embodiment, a sheet or belt of materialcapable of changing color upon application of a predetermined source ofsynergistic stimulation is used to provide an alphanumeric display alongthe conveyor belt. For example, a sheet of thermochromic material,capable of changing color upon the selective application of elevatedtemperature in a predetermined range may be used. Preferably, the sheetor belt of thermochromic material is coextensive with and driven by thesame transport means which conveys the items along the item path. In oneembodiment, a thermochromic material is contained in a sheet and changescolor from black to bright blue when the surface is heated to about 40to 45° C. To form a display, the surface of the sheet is selectivelyheated to form letters and numbers. Referring to FIGS. 7A-7D, a belt ofthermochromic material 70 is supported on a roller 72 for coextensivemovement with the transport means (not shown). The display material maybe, for example, any material capable of changing color in response toheat or to an applied electric current. The heating surface 76 comprisesan array of heating elements 77 disposed circumferentially around theroller. The heating elements 77 may be selectively activated by pulsingan electric current through brushes 78 in accordance with well knowntechniques. The brushes 78 are responsive to signals from the decodingmeans which in turn decodes the information supplied by the scanning ofthe bar code labels.

In accordance with well known techniques, the electric current isselectively pulsed to the brushes 78. The brushes in turn selectivelyactivate heating elements 77 to produce a pattern or visual displayimage of data associated with each item being scanned. It will beappreciated that the thermochromic material is capable of holding analphanumeric or other image display upon heating for a predeterminedamount of time without the need for being refreshed. Upon cooling, thethermochromic material simply reverts to its original color and is readyto be heated again to produce a visual display of data representative ofeach successive item being scanned by the scanning means 88 a.

An alternative embodiment of a display means is shown in FIG. 8A. Asheet or belt of liquid crystal material, such as noematic curvilinearaligned phase material (NCAP) 80 is supportably moved by a roller 81.The NCAP material is currently manufactured by at least three companies,Raychem, Taliq and Optical Shutters. Roller 81 moves the displayprovided by liquid crystal material 80 such that as the item moves downthe conveyor belt, the price and item name also are displayed on thesheet of liquid crystal material 80 and move with the item allowing thecustomer to see a description of the item and what amount is beingcharged for the item.

The sheet of liquid crystal material 80 includes on the front thereof,an array of pixel elements 82 or other display means for creating avisual pattern or alphanumeric image. An array of pixel elements 82comprise electrodes which effect the change in transmission of light andconsequently effect a change of color in the liquid crystal material 80.As shown in FIG. 8A, each row of pixel elements or electrodes 82 of thearray of pixel elements is disposed for contacting a correspondingactivating means 84. In a preferred embodiment, the activating meanscomprises a series of cylinders or rollers 84. The rollers 84 aredisposed on a single shaft 85 for contacting the liquid crystal material80. Each roller 84 is in turn selectively activated by microprocessor 86through an array of brushes 87 in accordance with well known techniques.The microprocessor 86 is responsive to a decoder 88 which decodes theinformation on the bar code label being scanned by the scanning means.As each roller 84 is selectively activated, it receives an appliedelectric current, and in turn, applies an electric charge to acorresponding one or more contacting pixel elements 82 in order to forma display image.

A suitable electrically activated liquid crystal material forapplication is sold under the trademark VARILITE, manufactured by TaliqCorporation of Sunnyvale, Calif., a subsidiary of Raychem. VARILITE orNCAP technology is based on the fact that the liquid crystals' moleculesorient themselves systematically with an electric charge and randomlywithout a charge, thereby selectively changing their ability to diffusethe transmission of light.

Referring to FIGS. 8B and 8C, the pixel elements 82 change theirstructural domains in response to an applied voltage, and thereby changecolor to form an alphanumeric display. A typical RC circuit foractivating the pixel elements is also shown in FIG. 8C. In thisembodiment, pixel elements 82 represent an array of electrodes on thecontrol electrode side of the film 80. A capacitance is formed by theindividual electrodes 82, an intermediate dielectric material 89 and acommon conductor 90 as shown. This forms a basic RC circuit. Theresistances R₁ and R₂ are inherent in the area of the film between theelectrodes 82. The values of the resistances R₁ and R₂ may be adjustedby selectively doping the material 80 in accordance with well knowntechniques. Making the value of R₂ smaller through deficient dopingallows a longer time constant. The RC circuit is activated by a signalfrom microprocessor 86 in response to decoding signals from the decoder88.

For example, once scanned and decoded, the item bar code information iscollected by a point of sale unit and the item description and price aredetermined in accordance with well known techniques. The description andprice information are applied to a microprocessor means which in turnactivates the display device to produce the desired display such as itemdescription and price. The display means of this embodiment provides anadvantage over conventional methods, such as an itemized listing,because the visual imagery is composed for easy understanding (and maybe in any language). The data display also moves along with the item onthe belt and therefore optimizes customer interpretation and providesminimum reading error. As shown in FIG. 1, the display mechanism 5visually displays an item description “CAKE MIX” and the price “1.25”.The data display (of item description “CAKE MIX” and the price “1.25”)moves in unison with the item I₁ on the conveyor belt C₁. Not only doesthis coordinated motion facilitate customer verification, but securityis facilitated allowing store personnel to readily monitor checkout toensure that the products are properly scanned and recorded. The datadisplay may be alphanumeric (e.g. “CAKE MIX” and price as in FIG. 1) orgraphical such as a pictorial representation of the item scanned. Suchpictorial confirmation is readily assimilated by the user.

The moving display is also advantageous over conventional itemized listsbecause it presents information within a fraction of a second from thetime that an item is scanned and continuously holds that information forthe customer, providing more time to read the data.

While the present invention has been described in connection with whatis presently considered to be the most practical and preferredembodiments, it is to be understood that the invention is not limited tothe disclosed embodiment but, on the contrary, is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims. For example, with regard to themoving display, a microprocessor may selectively activate certainbrushes which in turn activate selected heated zones to form a patternon a thermochromic material in accordance with decoding signals. Also,the display elements may be either passive electrochromic devices whichmodulate ambient light in response to decoding signals from the bar codescanners, or may be elements which actively emit light and change colorin response to an applied decoding signal such as an array of lightemitting diodes. However, in such a structure the display apparatus ismovably coupled to the transport belt to provide a moving display of theitem as it moves along the belt. Therefore, persons of ordinary skill inthis field are to understand that all such equivalent structures are tobe included within the scope of the following claims.

What is claimed is:
 1. A method for reading an item, comprising thesteps of reading the item from a first direction through a firstsurface; reading the item from a second direction, different than thefirst direction, through a second surface; determining distance from thefirst surface to the item and determining distance from the secondsurface to the item; adjusting an optical parameter for reading throughthe first surface based upon the distance determined from the firstsurface and separately adjusting an optical parameter for readingthrough the second surface based upon the distance determined from thesecond surface.
 2. A method according to claim 1, further comprisingarranging the first surface and the second surface on different sides ofa scan volume; passing the item through the scan volume on a conveyor.3. A method according to claim 2 further comprising reading through theconveyor.
 4. A method according to claim 1 further comprising arrangingthe first surface and the second surface generally orthogonally to oneanother.
 5. A method according to claim 1 wherein the step ofdetermining distance from the first surface to the item comprisesdetermining height of the item.
 6. A method according to claim 1 whereinthe step of reading the item from a first direction through a firstsurface comprises passing scanning beams through the first surface andinto the scan volume; wherein the step of adjusting an optical parameterfor reading through the first surface comprises adjusting focal distanceof the scanning beams being passed through the first surface.
 7. A datareading system according to claim 1 wherein the scanning mechanismcomprises a facet wheel having a plurality of mirror facets.
 8. A datareading system according to claim 1 further comprising a combiningelement located between the first laser diode and the scanning mechanismfor transmitting a light beam from the first laser diode through thecombining element to the scanning mechanism for reflection therefromalong a common path through the first window, the combining element alsobeing located adjacent the second laser diode for reflecting a lightbeam from the second laser diode entering the combining element to thescanning mechanism for reflection therefrom along the common path outthrough the first window.
 9. A data reading system comprising a housinghaving a first window and a second window arranged to face differentsides of a scan volume; a first set of pattern mirrors positionedadjacent the first window; a second set of pattern mirrors positionedadjacent the second window; a first laser diode pair comprising firstand second laser diodes and a second laser diode pair comprising thirdand fourth laser diodes within the housing; a scanning mechanism withinthe housing for scanning light from the first laser diode pair in a scanpattern out through the first window and for scanning light from thesecond laser diodes in a scan pattern out the second window, whereinsaid scanning mechanism reflects the light from the first and secondlaser diodes across the first set of pattern mirrors and out the firstwindow and reflects the light from the second laser source across thesecond set of pattern mirrors and out the second window, wherein thefirst and second laser diodes are focused at different focal positionswithin the scan volume and wherein the third and fourth laser diodes arefocused at different focal positions within the scan volume.
 10. A datareading system according to claim 9 wherein the first window and thesecond window are arranged generally orthogonally to one another.
 11. Amethod for scanning an item being passed through a scan volume,comprising the steps of producing a first set of scanning beams andpassing the first set of scanning beams through a first window and intothe scan volume; producing a second set of scanning beams and passingthe second set of scanning beams through a second window and into thescan volume; determining distance from the first window to the item anddetermining distance from the second window to the item; adjusting anoptical parameter of the first set of scanning beams based upon thedistance determined from the first window and separately adjusting anoptical parameter of the second set of scanning beams based upon thedistance determined from the second window.
 12. A method according toclaim 11 further comprising arranging the first window and the secondwindow on different sides of the scan volume; passing the item throughthe scan volume on a conveyor.
 13. A method according to claim 12further comprising reading through the conveyor.
 14. A method accordingto claim 11 further comprising arranging the first surface and thesecond surface generally orthogonally to one another.
 15. A methodaccording to claim 11 wherein the step of determining distance from thefirst window to the item comprises determining height of the item.